1. Field of the Invention
The present invention relates to the field of electronic packaging, particularly a method and resulting structure for a high speed chip carrier.
2. Description of the Related Art
High speed computers typically require minimal inductance of the supply power and ground loop for the integrated circuits (ICs) of the system. The ICs are usually mounted into chip carriers which have a plurality of leads that interconnect the chips and the signal, power and ground lines. The power supply leads are typically quite long, whereby there is created an unacceptable amount of inductance between the leads, particularly between the power and ground loop. This problem becomes greater as the speed of the system increases.
U.S. Pat. Nos. 4,891,687 and 4,835,120 issued to Mallik et al, discloses an IC package that has a pair of copper plates bonded to the lead frame of the package. The copper planes are separated by insulative material and have tabs that are connected to designated leads of the lead frame. The power and ground leads of the IC are attached to each conductive plate respectively. Power flows into the package, from the leads, through the plates and into the IC. The creation of separate power and ground planes reduces the inductance and increases the capacitance between power and ground lines. This reduction in impedance is particularly important for high speed circuitry.
Although the dual plane package provides a means of accommodating the noise created by high speed switching signal lines, the specific inductance and capacitance values are somewhat unpredictable because of the size and tolerances associated with the plates. Furthermore, there is no way of connecting passive components to the lead frame to customize the package. It would therefore be desirable to have an IC package that would allow the designer to control the impedance and thus reduce the creation of noise of the circuit within the package. It would also be desirable to have a method of constructing an IC package that can provide internal routing with the package.